Members of the large SOX family of transcription factors are widely conserved and at least 20 are found in mammals. Structurally SOX proteins exhibit a high mobility group (HMG) motif that binds the DNA minor groove. SOX family members are often found in multiprotein complexes that regulate their ability to affect transcription. SOX proteins play important roles in early development and are often used as markers to assess the differentiation of specific cell lineages.
SOX1 (SRY-related HMG box 1) is a 39 kDa transcription factor that belongs to the SRY family of HMG box proteins. Group B contains SOX1 along with SOX2, SOX3, SOX14, and SOX21; each of these factors share greater than 90% homology in their respective HMG box region. SOX1 maintains neural cells in an undifferentiated state and has been used as a marker for neural stem cells. Human and mouse SOX1 share 97% amino acid sequence identity.